In Situ Ligand Formation in the Synthetic Processes from Mononuclear Dy(III) Compounds to Binuclear Dy(III) Compounds: Synthesis, Structure, Magnetic Behavior, and Theoretical Analysis

Guided by the self-assembled process and mechanism, the strategy of in situ Schiff base reaction would be capable of bringing a feasible method to construct and synthesize lanthanide compounds with distinct structures and magnetic properties. A mononuclear Dy(III) compound was synthesized through a multidentate Schiff base ligand and a chelating beta-diketonate ligand, which was named as [Dy(L)(bppd)]center dot CH3OH [1; H2L = N,N'-bis(2-hydroxy-5-methyl-3formylbenzyl)-N,N'-bis(pyridin-2-ylmethyl)ethylenediamine and bppd = 3-bis(pyridin-2-yl)propane-1,3-dione]. Furthermore, a new binuclear Dy(III) compound, [Dy2(H2Lox)(bppd)3]center dot 8CH(3)OH [2; H4Lox = N,N'-bis[2-hydroxy-5methyl- 3-(hydroxyiminomethyl) benzyl]- N,N'- bis( pyridin- 2- ylmethyl)ethylenediamine], was obtained via an in situ synthetic process. Under similar synthetic conditions, [Dy(L)(ctbd)] [3; ctbd = 1-(4-chlorophenyl)-4,4,4-trifluoro1,3-butanedione] and [Dy-2(H(2)Lox)(ctbd)(3)]center dot CH3OH center dot C4H10O (4) were synthesized by modifying the beta-diketonate ligand and in situ Schiff base reaction. Compound 3 is a mononuclear configuration, while compound 4 exhibits a binuclear Dy(III) unit. Therein, formylbenzyl groups of H2L in 1 and 3 were changed to (hydroxyiminomethyl)benzyl groups in 2 and 4, respectively. In isomorphous 2 and 4, two Dy(III) centers are connected through two phenol O- atoms of the H(2)Lox(2)(-) ligand to form a binuclear structure. Eight-coordinated Dy(III) ions with different distortions can be observed in 1-4. The crystals of 1 and 3 suffered dissolution/precipitation to obtain 2 and 4, respectively. The relationship between the structure and magnetism in compounds 1-4 was discussed through the combination of structural, experimental, and theoretical investigations. Especially, the rates of quantum tunneling of magnetization of 1-4 were theoretically predicted and are consistent with the experimental results. For 2 and 4, the theoretically calculated dipolar parameters Jdip are consistent with the experimental observation of weak ferromagnetic coupling.

Automated summary

Guided by the self-assembled process and mechanism, the strategy of in situ Schiff base reaction successfully synthesized lanthanide compounds with distinct structures and magnetic properties, including mononuclear and binuclear Dy(III) compounds.